The petrochemical and refining industries generally employ various processes where temperature must be measured reliably and accurately. Many of these processes involve treatment of a hydrocarbon material using various catalytic processes that are carried out in a reactor vessel. Typically, such processes involve reacting the hydrocarbon material with hydrogen in a series of catalyst beds, each of which is made up of a material that is suited for the type of hydroprocess performed in the particular bed. These processes are performed at high temperatures, which must be monitored and controlled to ensure that the process is carried out efficiently, but safely without damaging either the vessel or the materials that make up the catalyst beds.
A variety of temperature sensors have been used in conjunction with these processes. For example, temperature sensors can be deployed in a catalyst bed to monitor the temperature of the catalyst for the purpose of maintaining control of the temperature of the process, maximizing the use of the catalyst and/or projecting the remaining useful life of the catalyst. Other temperature sensors can be used to monitor the outer surface (or skin) of a high temperature vessel or tubes or other conduits that are present within a furnace used in a refining process to ensure both that the structure is not overheating and that the process is occurring at a desired temperature. However, neither of these types of arrangements of sensors can provide accurate measurements of the temperature of the inner wall of a high temperature vessel. For instance, while a temperature sensor embedded in the catalyst bed can provide information about the temperature of the process occurring in the bed, it can provide only an approximation of the temperature of the inner wall of the vessel. Similarly, sensors that monitor temperature of the outside wall of the vessel can provide only an approximation of the temperature of the inner wall.
Knowledge of the actual and real-time temperature of the inner wall of a high temperature vessel can lead to more well-informed decisions by an operator of a high temperature vessel. As an example, if the operator is confident that the temperature sensing assembly is providing an indication of the actual temperature of the inner wall (as opposed to an approximation), then the process being performed in the vessel can be implemented at as high of a temperature as possible to obtain maximum yield without concern that the structure of the vessel itself may be overheating. Further, real time measurements of the actual temperature allow the operator to more quickly take remedial actions in the event of a hazardous situation. As an example, during some hydrocarbon processes, petroleum coke accumulations (or coke-ball build ups) may occur within the reactor. Although the coke accumulations can be benign, they also can cause failures if they are near or move towards the reactor wall. Accurate and real-time information about the temperature of the reactor wall (and thus the integrity of the reactor) can allow the operator to attempt to lower the temperature of the process by applying a quenching fluid or to take other actions to safeguard the environment and the workers.